1. Technical Field
2. Field of the Present Invention
The present invention relates to a positioning method and system for land and water vehicles, and more particularly to a self-contained positioning method and system for land and water vehicles, wherein output signals of an inertial measurement unit, an odometer, a velocimeter, and a magnetic sensor are processed to obtain highly accurate position measurements of a vehicle on land and in water.
3. Description of Related Arts
Nowadays, GPS (Global Positioning System) is the most accurate navigational system available for commercial uses. The GPS is a satellite radio-navigation system, which is owned, deployed, and operated by the U.S. Department of Defense, but is available for commercial uses around the world.
GPS has 21 GPS satellites and three spare satellites in orbit at 10,600 miles from the Earth. The satellites are spaced so that from any point on Earth, four satellites will be visible above the horizon. Any GPS receiver on ground, air, and near space contains a microprocessor that xe2x80x9ctriangulatesxe2x80x9d its own position by getting bearings and ranges from four GPS satellites. The result is provided in form of a geographic positionxe2x80x94longitude and latitude as well as altitudexe2x80x94within 100 meters accuracy, for most receivers.
A conventional, single-antenna, typical GPS receiver can supply world-wide highly accurate three dimensional position, velocity and timing information, but not attitude, by processing so-called pseudo-range and pseudo-range rate from individual code tracking loops and carrier tracking loops respectively. In benign radio environment, the GPS navigation errors are bounded primarily by the GPS signal propagation and satellite errors.
Unfortunately, GPS is vulnerable to jamming and shadowing, especially on land and in water, so that a GPS receiver is not often able to provide continuous positioning information.
An inertial navigation system is a self-contained navigation system. But, the effectiveness of the inertial navigation system diminishes in land and water due to its positioning accuracy drift with time.
Therefore, it is very desirable to develop a positioning system, which can be used in areas where GPS signals are not available, such as buildings, tunnels, forested areas, and high Electronic Counter Measure (ECM) environments.
The main objective of the present invention is to provide a self-contained positioning method and system to determine position of a vehicle on land and in water with high accuracy such as an accuracy of better than one percent of the distance traveled without using GPS or radar updates, wherein output signals of an inertial measurement unit, an odometer, a velocimeter, and a magnetic sensor are processed to obtain highly accurate position measurements of the vehicle on land and in water. The present invention functions as an integrated micro land and water navigator, which has the following unique features:
(1) Miniature, light weight, low power, low cost.
(2) MEMS IMU (MicroElectroMechanicalSystem Inertial Measurement Unit), odometer, velocimeter, and magnetic sensor.
(3) Integration filter for sensor data fusion and zero velocity updating.
Typical applications include automobiles, railway vehicles, miniature land vehicles, robots, unmanned ground vehicles, personal navigators, military land vehicles, and marine vehicles.